esertification in China is acceler- ating in the northern provinces, stretching from the western border to the capital (Figure 1). Centres of desertification are Xinjiang, Inner Mongolia, Tibet, Gansu, Qinhai, Shannxi, Ningxia, and Hebei province. The desertifica- tion belt is located in the arid and semi-arid zone of China. Here the desert margins are vulnerable to inappropriate land-use and climate change. The area of arid, semiarid and dry sub-humid regions is approximately 3.32 million km 2 , of which 2.62 million km 2 (79 %) has been desertified. This amounts to 27.3 % of China’s territory. Human-induced desertification has often completely destroyed the natural vegetation cover. One of the major threats for the entire region, which is closely connected with desertification, is sand and dust storms from the Gobi desert (see also contribution by Littmann and the Map Insert in this issue) and other regions with wind erodible surfaces. These storms periodically return in winter and spring. Since the 1950s a drastic increase in the occurrence of dust storms can be observed. In the 1950s the number of dust storms was only five per year whereas in the year 2000 in a 45 day period alone eight dust storms were recorded in Northern China. On 5 May 1993 during such a dust storm in Xinjiang, Gansu, Inner Mongolia and Ningxia provinces, 85 people lost their lives, 31 people went missing and 264 were injured (Yang et al. 2001). 120,000 head of cattle were killed. The damage by erosion and land degradation as well as the economic loss was immense. The dust storms not only affect the rural areas but also large cities like Beijing. Their traces are spread across the northern hemisphere. It is estimated that the immediate economic damage through deserti- fication in Northern China, which is the least developed part of the People’s Republic, is more than 500 million each year. This sum does not include the ecological impact and the loss of natural resources. Those indirect damages may be as much as two or three times that of the direct damage. 14 Geographische Rundschau International Edition Vol. 2, No. 3/2006 The Green Great Wall – Combating Desertification in China Photo 1–7: M. Veste Photo 1: Mobile sand dunes in the Tengger desert near the Yellow River (Inner Mongolia) MAIK VESTE, JIARONG GAO, BAOPING SUN, SIEGMAR-W. BRECKLE D Desertification of drylands is a global problem in both developed and developing countries. Desertification affects human life on many levels. China is one of the seriously affected countries with vast areas of desertification. Dust and sand storms are threats for drylands as well as for megacities. Dust is transported over vast distances. During the past decades major measures to combat desertification were established in the northern provinces. Those include vegetation shelterbelts and reforestation of desertified lands to reduce soil erosion and to stabilize sand dunes. lizensiert f¨ ur M Veste am 21.10.2012 lizensiert f¨ ur M Veste am 21.10.2012
Transcript
esertification in China is acceler-ating in the northern provinces,stretching from the western borderto the capital (Figure 1). Centres of desertification are Xinjiang,Inner Mongolia, Tibet, Gansu,Qinhai, Shannxi, Ningxia, and
Hebei province. The desertifica-tion belt is located in the arid andsemi-arid zone of China. Here thedesert margins are vulnerable toinappropriate land-use and climatechange. The area of arid, semiaridand dry sub-humid regions isapproximately 3.32 million km2, of which 2.62 million km2 (79 %)has been desertified. This amountsto 27.3 % of China’s territory.
Human-induced desertificationhas often completely destroyed the natural vegetation cover. Oneof the major threats for the entireregion, which is closely connectedwith desertification, is sand anddust storms from the Gobi desert(see also contribution by Littmannand the Map Insert in this issue)and other regions with winderodible surfaces. These stormsperiodically return in winter andspring. Since the 1950s a drasticincrease in the occurrence of duststorms can be observed. In the1950s the number of dust stormswas only five per year whereas in
the year 2000 in a 45 day periodalone eight dust storms wererecorded in Northern China.
On 5 May 1993 during such a dust storm in Xinjiang, Gansu,Inner Mongolia and Ningxiaprovinces, 85 people lost theirlives, 31 people went missing and264 were injured (Yang et al.2001). 120,000 head of cattle werekilled. The damage by erosion andland degradation as well as theeconomic loss was immense. Thedust storms not only affect therural areas but also large cities likeBeijing. Their traces are spreadacross the northern hemisphere. It is estimated that the immediateeconomic damage through deserti-fication in Northern China, whichis the least developed part of thePeople’s Republic, is more than ! 500 million each year. This sumdoes not include the ecologicalimpact and the loss of naturalresources. Those indirect damagesmay be as much as two or threetimes that of the direct damage.
14 Geographische Rundschau International Edition Vol. 2, No. 3/2006
The Green Great Wall – CombatingDesertification in China
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7: M
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Photo 1: Mobile sand dunes in the Tengger desert near the Yellow River (Inner Mongolia)
M A I K V E S T E , J I A R O N G G A O, B A O P I N G S U N, S I E G M A R - W. B R E C K L E
D
Desertification of drylands is a global problemin both developed and developing countries.Desertification affects human life on manylevels. China is one of the seriously affectedcountries with vast areas of desertification.Dust and sand storms are threats for drylandsas well as for megacities. Dust is transportedover vast distances. During the past decadesmajor measures to combat desertification were established in the northern provinces.Those include vegetation shelterbelts andreforestation of desertified lands to reduce soil erosion and to stabilize sand dunes.
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Desertification not only causesland degradation but affects localground water resources and riversas well. Soil erosion transportstremendous amounts of silt to theriverbeds. The Great River wasrenamed the Yellow River after theincreased transportation of loessicmaterials. Very often the rivers dryout and the ground water tabledrops down due to the overuse ofthe water resources for irrigation.Water shortage enhances deserti-fication processes and the destruc-tion of vegetation belts.
Combating desertification in ChinaIn recent decades the Chinesegovernment has become con-cerned about the environmentalsituation and has established
several reforestation programmesand promoted scientific researchon the desertification process andhow to combat it (Sun and Fang2001). The “Green Great WallPlan” was launched in 1978 torestore the vegetation in the north-ern provinces and to protect the
cities from sand and dust storms.In 1991 the “China DesertificationRehabilitation and Desert Recla-mation Action Programme”started to operate. It is one of themajor engineering projects tostabilize the ecosystems in China.Besides technical measures the
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Desertification Area (km2) Desertification Area (km2)causes 1999 2004 degrees 1999 2004
Table 1: The status of desertification in China, 1999 and 2004
Figure 1: Desertification regions in ChinaThe most affected areas are in the arid and semi-arid provinces in northern China
Design: Gao and Sun
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Chinese Government has formu-lated and promulgated laws, poli-cies and regulations regarding the prevention and control ofdesertification, such as the ForestLaw, the Law of Soil and WaterConservation, the Water ResourceLaw, the Law of EnvironmentalProtection, etc.
In the past years noticeableprogress is being made in reducingdesertification. In 2004 the totalarea effected by desertification inChina was 37,924 km2 less than in 1999 (Table 1). However, thisreduction amounts only to 1.4 % of the total desertified area. There-fore combating desertification still remains a challenge. The bestachievements were made in thestabilisation of seriously effectedareas; here the reduction wasnearly 19 %.
Sand dune fixationShifting sands are one of the major problems of desertificationand land degradation in arid andsemiarid areas. Sand dune move-ment is a threat to irrigatedfarmlands, villages, railways, high-ways and other infrastructure.Sandy areas cover large parts ofChina’s deserts from the hyper-arid zones in the west to the semi-arid regions in the east. Therefore,most investigations focus on deser-tification processes and rehabilita-tion of sandy areas.
Highly mobile dunes are char-acteristic of the Tengger desert(Photo 1). The average annualprecipitation at the southern edgeis approximately 180 mm andvaries between 80 and 300 mm per year depending on the mon-soon. The rainy season is betweenMay and September. The meantemperature in July is 24.3 °C and–6.9 °C in January.
Historic records show thatthese regions were vegetated cen-turies ago. In 428 AD shrubs andgrasses covered the Mu Us sand-land west of the Tengger desert.However, the capital was alreadyburied due to desertification only500 years after its establishment.In recent times most of the dunesare bare of vegetation and are
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The Green Great Wall – Combating Desertification in ChinaM . V E S T E , J . G A O, B. S U N, S. - W. B R E C K L E
Photo 3: Stabilised sand dunes at the Yellow River along the railway Beijing-Lanzhou
Photo 4: Microbiotic soil crust on sand dunes in the Tengger desert
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highly mobile. Average wind speed is around 3.5 m per secondprimarily from a northwesterlydirection. The relatively high pre-cipitation of more than 180 mmper year should promote a vegeta-tion cover, but it seems that thefrequent high wind speeds counterthe re-establishment of naturalvegetation.
Several experiments have been made regarding sand dunestabilization worldwide. Plantingmethods are a traditional means to control drifting sands and arewidely practiced. However, sanddune fixation by vegetation is only successful when wind speedis greatly reduced and sand move-ment is minimized. For dune sta-bilisation a combination of windbreaks, straw checkerboards andplanted shrubs is used (Photo 2).In the first stage straw checker-boards are installed manually toincrease surface roughness anddecrease sand transportation. An efficient straw checkerboard is 10 to 20 cm in height and 1 x 1 m in size (Qiu et al. 2004).The checkerboard can cause thedeposition of blown sand (includ-ing seeds) and decrease the sandflow by more than 99.5 % (Figure2). Since 1957 this system wassuccessfully tested in the sanddunes of northern China to protectthe railway line from Baotou toLanzhou. In Shapatou the vegeta-tion protection system is 16 kmlong and 500 m wide on thenorthern and 200 m wide on thesouthern side of the railway.
Meanwhile the straw checker-board is widely used for sand dune fixation. However the instal-lation and maintenance of thecheckerboard is labour intensive.In the Tengger desert the low rain-fall limits tree planting but pro-motes shrubs, grasses and herbs(Photo 3). In the centre of thecheckerboards were planted main-ly seedlings of Artemisia ordosica,Hedysarum scoparium, Caraganakorshinskii, Eragrostis poaeoidesand Calligonum mongolicum.Other plants, especially annuals,became established naturally.
Most remarkable is the devel-opment of biological soil crusts on
the stabilised sand surface betweencheckerboards and shrubs (Photo4). These biological soil crusts(also called microbiotic, micro-phytic or cryptogamic crusts) cov-er the upper millimetres of topsoil.They are build up by cyanobacte-ria, green algae, mosses, fungi as well as lichens. Such biologicalsoil crusts can be found in manyarid and semi-arid regions. Forexample, most parts of the Negevsand dunes in Israel are coveredby cyanobacterial and soil lichenscrusts (Veste and Breckle 2000).They are one of the first colonizersof disturbed soils.
In the Tengger desert soil crustscan be found on stabilized plots.With time the composition of thecrusts changes and a successiontakes place. The first colonizersare cyabobacteria which stabilizethe sand surface. In the later stagesmosses are able to grow (Figure3A). The biological soil crusts areimportant for soil developmentand strongly influence hydrologi-cal processes (Veste et al. 2001,Veste 2005). Several studiesshowed that biological nitrogenfixation by free-living and symbi-otic cyanobacteria is a majornitrogen source and contributes up to 60 % into this nutrient-poorecosystem. The cyanobacteriaexcrete exo-polysaccharids whichcause the soil and sand particles to stick together. This enhancessurface stability and prevents winderosion of the sand surface.
On the other hand the biologi-cal soil crusts have negative effectson seedling establishment and on hydrological processes. In gen-eral crusting of soil surfaces limitsinfiltration and increases runoff.Upon wetting the biological soilcrusts absorb rainwater followedby swelling of the silt and clayeyparticles and biological elements.This results in a decrease of poresize and thus limits infiltration. In the sand dunes near Shapatou(Inner Mongolia), it could beobserved that moisture retentionby fine grain material influenceswater infiltration to deeper depthswhich may lead to a decliningnumber of deep-rooting shrubs(Figure 3A). Mosses especially
enhance this negative effect whilecontaining a high amount of finematerial.
Reforestation projectsThe unsustainable use of forestresources leads also to a shortageof timber and trees for fuel woodin China. How drastic the changes
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Figure 2: Relation between wind speed and sand fluxesin a shifting sand dune area and a 1 x 1 m checkerboardarea. Note that straw checkerboards prevent sand fluxup to a wind speed of 6.25 m per second Source : Qiu et al. 2004
Figure 3: Cyanobacterial crusts and mosses (A) and veg-etation cover with shrubs, grasses and other annuals onmobile and stabilised dunes (B) near Shapotou (Tenggerdesert), representing different surface ages (0, 12, 29,37 years in 1993) Note that mosses prevent water infiltration and reduce water availabilityfor deep rooting shrubs which decline over time
Source: Fearnehough et al. 1998
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in the forest cover in the last cen-turies have been can be demon-strated in the Loess Plateau. The Loess Plateau is one of thecentres of the development of theChinese civilization. During theMing Dynasty (1368–1644) andthe Qing Dynasty (1644–1911),the forestry coverage on theplateau was around 15 %. In 1949 the forest cover had beenreduced to 3 % due to forest cut-ting and lumbering. Large-scalesoil erosion was the consequence.Therefore, the re-establishment of forest systems was a major goal in China’s programme tocombat desertification.
One of the most efficient sys-tems is planting trees and shrubsto form shelterbelts (Photo 5). Treeshelterbelts are one of the majorcomponents in building a “GreenGreat Wall”. These huge protec-tive forest systems are set up toconserve soil and water and pre-vent damage from desertification.The major protective forest sys-tems are: • the “Three Norths” protective
forest system, • the protective forest system in
the middle and upper reachesof the Yangtze River,
• the coastal windbreak systemand
• the farmland shelterbelts in theplains.
Sanbei or “Three Norths”protective forest systemThe Sanbei shelter forest is one ofthe largest re-forestation projects.Sanbei means “Three Norths” andrefers to the provinces in north-western, northeastern and north-ern China (Figure 1). It extends4,480 km in length from east towest, and is 400–1,700 km widefrom north to south covering 551 counties in 13 provinces andaccounting for 42 % of the totalterritory of China. In these vastareas the farmland suffers from
wind and sand damage whichamounts to 6.7 million hectares(ha) making up 40 % of the totalfarmlands in China.
In order to deal with such aserious situation, the Chinesegovernment decided to launch the“Green Great Wall” on a largescale. In the first phase of theproject (1978–1985), an area of6.06 million ha was planted, ofwhich 63.8 % is windbreak. Theforest coverage of the “ThreeNorths” region reached by the endof the first phase was 6.2 %. Sincethe second phase (1986–1995) theestablishment of a network offarmland shelters is combined withthe introduction of commercialforestry. In this period the forestcover increased to 7.9 %.
According to a survey about 12 % of desertified lands are nowcompletely under control of anti-desertification measures, andanother 10 % of desertified landswill be soon under control. It isestimated that by the end of theproject in 2050 5.23 million ha oftree plantations will have beencompleted.
Farmland shelterbelt A farmland shelterbelt was suc-cessfully established in the Horqinsandy land in the semi-arid north-east of China. The Horqin sandyland stretches over 42,300 km2
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The Green Great Wall – Combating Desertification in ChinaM . V E S T E , J . G A O, B. S U N, S. - W. B R E C K L E
Photo 5: Forest shelterbelt around Beijing
Photo 6: Planting of trees is important to improve the local climaticconditions in the villages
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(area northeast of Beijing in Figure 1) in the transitional zonebetween semi-arid and the sub-humid with annual rainfall be-tween 315 and 490 mm. It receives90 % of the precipitation in thegrowing season between April andSeptember. In the past the Horqindistrict was fertile farmland andpastures. Its original vegetationwas steppe with typical grasslandvegetation. Dominant species ofthis region include Stipa grandis,Leymus chinensis and Agropyroncristatum. Desertification tookplace due to forest cuttings andovergrazing, and the area wasrenamed “sandy land”. The sandy areas are threatening vil-lages, fields and infrastructure.Shelterbelts were designed to pro-tect the villages against local sandstorms and to reduce soil erosion(Photo 6). Mainly fast growingpoplar species, including nativespecies such as Populus pseudosi-monii, P. simonii and some otheruseful domestic and foreign poplarspecies, including P. deltoides, P. trichocarpa and P. nigra, areused for construction of the shel-terbelt (Photo 7). Also differentconifer species were introduced.Several tree species originatedfrom Europe and North Americaand lead to changes in speciescomposition.
Besides the functions of treeshelterbelts for soil protection, thenewly established forests are alsoimportant for timber productionand as a firewood source for localmarkets. This is closely related to commercial timber processingand the establishment of ruralenterprises. Leaves of poplar, wil-low and Ulmus are used as forageresources for animal husbandry. In the Shanxi Provinces 40,000 haof Caragana shrubs were plantedto use as fodder for sheep grazing.Nowadays, the Sanbei district hasturned into an important producerof fruits, including apples, apricots,chestnuts, Chinese red dates(Elaeagnus), pears, seabuckthorn(Hippophae) and walnuts. InHebei province viniculture andprocessing were promoted. Fromseabuckthorn more than 200 prod-ucts are made for health foods,
cosmetics and medicines. The fruitproduction creates new jobs andincome for the local people.
Combating desertification on the Loess PlateauThe Loess Plateau is a vast areawhich extends around midstreamof the Yellow river (Figure 1),occupying about 580,000 km2.There are about 60 million peopleliving on the plateau and a largenumber of them are forced to live in poverty in caves (calledYaodong). The Loess Plateau isconsidered to have been formed byan accumulation of a huge volumeof loess with a thickness of 50 to100 m brought in to this regionfrom the northwestern deserts bystrong winds 1.2 million years ago.In prehistoric times the area wascovered with rich vegetation, butthe increase in population sincethe 11th century promoted defor-estation and the development ofgrasslands on a large scale. As aresult the balance of the ecosys-tems got completely lost, and theregion has been facing extremeerosion problems (Photo 8).
The Loess Plateau has an alti-tude between 1,000 and 2,000 mabove sea level. The annual meantemperature is between 4 and 7º C and annual precipitation is between 300 and 450 mm. 60–70 % of the rainfall takes place
between July and September in the form of torrential rains causingserious soil erosion. The annualamount of soil erosion is one ofthe highest in the world and is said to amount to 1,100 to 9,600tons per km2.
The growth of 20,000 plantspecies collected inside and out-side of China has been studied forseveral years. They were seeded inexperimental fields. Most species
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Figure 4: Effect of plowing, grazing and seeding varia-tions on soil and water outflow in the Loess Plateau. For grass seedings Stipa bungeana, Bromus inermis andPanicum virgatum were used. Panicum reaches a heightup to 1.2 m, Stipa and Bromus of 20–25 cmSource: Ichizen 2003
Photo 7: Shelterbelt with poplar trees in Inner Mongolia
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were not suitable. Several perenni-al grasses grew well. The adapt-ability of 197 grass species wastested in pasture trials. 20 speciesgrew for five years after seeding(Figure 4). Panicum virgatumexhibited by far the most denseplant cover and greatest height.New projects are on the way toreach again a closed vegetationcover and to reduce erosion byextensive plantings of trees, oftenalong new small terraces and byseeding grasses.
Biodiversity and ecosystemfunctioning – a perspective It can be concluded that for ashelterbelt design and the reha-bilitation of drylands a specificknowledge of natural ecologicalprocesses is needed. The presentmeasures in place to combat de-sertification are focussed on therapid development of sufficient
shelterbelts to reduce soil erosionas well as dust and sand storms.However, monocultures of only a few species will lead to adecline in biodiversity, and theyare threatened by future climatechange, pests or herbivory. Evenworse the introduction of alienspecies causes adverse effects inevery ecosystem. Therefore futurerehabilitation concepts need toinclude the indigenous biodiversityand the mechanisms of the eco-system in order to create self-sus-taining ecosystems. In China “gowith nature” will be a major chal-lenge for the improvement of shel-terbelts against desertification. !
ReferencesFearnehough, W., M.A. Fullen, D.J. Mitchell,
I.C. Trueman and J. Zhang 1998: Aeoliandeposition and its effect on soil and vegeta-tion changes on stabilized desert dunes innorthern China. Geomorphology 23, pp. 171–182
Ichizen, N. 2003: Vegetation recovery in loessplateau in China. Global perspective inrange rehabilitation and prevention of deser-tification. In: 2003 Obihiro Asia and PacificSeminar on Education for Rural Develop-ment (ed. J. Takahashi) OASERD ObihiroUniversity, Japan, pp. 45–49
Li, Z. and W. Shi 2003: Analysis of water con-sumption of artificial sand-fixing plants andsimulation of ecological moisture fitness. Israel Journal of Plant Sciences 51 (2), pp. 101–108
Li, X.-R., X.-P. Wang, T. Li and J.G. Zhang2002: Microbiotic soil crust and its effect onvegetation and habitat on artificially stabi-lized desert dunes in Tengger Desert, NorthChina. Boil. Fertil. Soils 35, pp. 147–154
Qiu, G.Y., I.B. Lee, H. Shimizu, Y. Gao and G. Ding 2004: Principles of sand dune fixa-tion with straw checkerboard technologyand its effects on the environment. J. AridEnvironm. 56, pp. 449–464
Sun, B. and T. Fang 2001: Desertification inChina and its control. In: S.-W. Breckle, M. Veste and W. Wucherer (eds.): Sustain-able Land-Use in Deserts. Heidelberg, Berlin,New York, pp. 357–367
Veste, M. 2005: The importance of biologicalsoil crusts for rehabilitation of degraded aridand semi-arid ecosystems. Science of Soiland Water Conservation 3 (4), pp. 42–47
Veste, M. and S.-W. Breckle 2000: Die Negev –Pflanzenökologische und ökosystemareBetrachtungen. Geographische Rundschau52 (9), pp. 24–29
Veste, M., T. Littmann, S.-W. Breckle and A. Yair 2001: The role of biological soilcrusts on desert sand dunes of the north-western Negev (Israel). In: S.-W. Breckle, M. Veste and W. Wucherer (eds.): Sustain-able Land-Use in Deserts. Heidelberg, Berlin,New York, pp. 357–367
Yang, G., H. Xiao and W. Tuo 2001: Blackwindstorm in northwest China – a casestudy of the strong sand-dust storm on May5th, 1993. In: UNCCD Global Alarm: Dustand sandstorms from the world’s drylands.Bonn, pp. 49–73
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The Green Great Wall – Combating Desertification in ChinaM . V E S T E , J . G A O, B. S U N, S. - W. B R E C K L E
Dr. Maik Veste (see page 7)
Prof. Dr. Jiarong Gao and Prof. Dr. Baoping SunCollege for Soil and Water Conservation, Beijing Forestry University, 35 Qinghua EastRoad, Haidan District, 100083 Beijing / PEOPLE’S REPUBLIC OF CHINAE-Mail: [email protected]
Professor Dr. Siegmar-W. BreckleLehrstuhl für Ökologie, Universität Bielefeld,Postfach 10 01 31, 33501 Bielefeld / GERMANYE-Mail: [email protected]
Authors
Photo 8: Soil erosion on the Loess Plateau
Phot
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.-W
. Bre
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